Ceratoplax margarita, Ng & Clark, 2015

Ng, Peter K. L. & Clark, Paul F., 2015, Ceratoplax margarita n. sp., a new rhizopine crab (Crustacea: Brachyura: Pilumnidae) from Papua New Guinea, with rediagnoses of C. truncatifrons Rathbun, 1914, and C. fulgida Rathbun, 1914, Zoosystema 37 (2), pp. 323-331 : 328-331

publication ID	https://doi.org/ 10.5252/z2015n2a2
publication LSID	urn:lsid:zoobank.org:pub:DF6FC413-9BD1-459B-BC25-FB8F6A0FD339
persistent identifier	https://treatment.plazi.org/id/D4F148DA-CC5A-4D05-AC24-0C3B21FD5F67
taxon LSID	lsid:zoobank.org:act:D4F148DA-CC5A-4D05-AC24-0C3B21FD5F67
treatment provided by	Felipe
scientific name	Ceratoplax margarita
status	sp. nov.

Treatment

Ceratoplax margarita View in CoL n. sp.

( Figs 5 View FIG ; 6 View FIG )

TYPE MATERIAL. — Holotype: Papua New Guinea, ♂, 7.9 × 5.2 mm (MNHN-IU-2014-10126), stn DW3663, Open Bay , 04°50’S, 151°39’E, 220-292 m, 23.IX.2010, Cruise BIOPAPUA, R. V. Alis, coll. S. Samadi & L. Corbari. GoogleMaps

ETYMOLOGY. — The Latin name, margarita , name alludes to the white, pearl-like appearance of the species. The name is used as a noun in apposition.

DIAGNOSIS. — Carapace transversely subovate, width 1.52 × length; dorsal surfaces smooth, glabrous, regions poorly demarcated, H-shaped gastric grooves barely discernible; anterolateral margin strongly convex, entire to weakly dentate with three small clefts, reaching along ⅔ of lateral margin, submarginal parts smooth, not clearly demarcated from posterolateral margin; posterolateral margins gently concave, converging to gently convex posterior carapace margin ( Fig. 5A View FIG ). Frontal margin weakly divided into two low subtruncate lobes from dorsal view, gently confluent with supraorbital margin; with low external orbital tooth ( Fig. 5A View FIG ). Orbit ovate, small, eyes with small cornea, fused to carapace, immovable ( Fig. 5B View FIG ). Posterior margin of epistome gently convex, not clearly divided into lobes ( Fig. 5B View FIG ). Anteroexternal angle of merus of third maxilliped with auriculiform structure; exopod stout ( Fig. 6F View FIG ). Male thoracic sternum wide, sternites 1 and 2 completely fused to form wide triangular structure; separated from fused sternites 3 and 4 by distinct sinuous suture ( Fig. 5C View FIG ). Male abdomen

T-shaped; somite 6 rectangular, wider than long; telson triangular, elongate, much longer than somite 6 ( Fig. 5C View FIG ). Chelipeds stout, carpus with subdentiform inner angle and tuft of setae, outer angle sharp but not spiniform or dentiform; chela stout, fingers shorter than palm ( Fig. 5A, B View FIG ). Ambulatory legs, long; articles slender, unarmed; dactylus of last leg upcurved ( Fig. 5A View FIG ). G1 distinctly sinuous, subdistal part hump-like with tapering tip which is gently bent, opening slender ( Fig. 6 View FIG A-D).

TYPE LOCALITY. — Open Bay, 04°50’S, 151°39’E, Papua New Guinea.

DISTRIBUTION. — Known only from the type locality.

REMARKS

There are many superficial similarities between Ceratoplax margarita n. sp., C. truncatifrons and C. fulgida . The series of specimens of C. truncatifrons from Indonesia show that the diagnostic characters of this species are quite consistent, notably in the general shape of the carapace ( Figs 1 View FIG ; 2 View FIG ). Although the proportions change, being relatively broader in larger specimens (e.g., Figs 1A View FIG ; 2C View FIG ), the shape remains unchanged. The structure of the thoracic sternums is also quite consistent, although the male telsons are slightly more elongate in the larger males ( Fig. 1C View FIG ) compared to the more evenly triangular ones in smaller ones ( Fig. 2D, E View FIG ). In C. fulgida , the anterolateral margin may appear to be entire ( Figs 3A View FIG ; 4H View FIG ) or weakly dentate ( Fig. 4I View FIG ).

Ceratoplax margarita n. sp. can be distinguished from C. truncatifrons and C. fulgida in having its posterolateral margin more distinctly converging towards the posterior carapace margin ( Fig. 5A View FIG ) (weakly converging in the other two species; Figs 1A View FIG ; 2 View FIG A-C; 3A). In addition, the anteroexternal angle of the merus of the third maxilliped of C. margarita n. sp. is auriculiform ( Fig. 6F View FIG ), resembling that of C. fulgida ( Fig. 4G View FIG ) but different from C. truncatifrons that has the anteroexternal angle prominently elongate ( Fig. 4C View FIG ). The sternoabdominal cavity of C. margarita n. sp. reaches to the median part of fused thoracic sternite 3 and 4, at an imaginary line connecting bases of coxae of chelipeds ( Fig. 5C View FIG ) (like in C. truncatifrons , Figs 1C View FIG ; 2D, E View FIG ) but in C. fulgida , it reaches up to two-thirds of fused thoracic sternites 3 and 4, to an imaginary line connecting midpoints of bases of cheliped coxae ( Fig. 3C View FIG ). The G1 of C. margarita n. sp. is relatively stout ( Fig. 6A, B View FIG ), but is distinctly more slender in C. truncatifrons ( Fig. 4A, B View FIG ). In stoutness, the G1 of C. margarita n. sp. looks more like that of C. fulgida but has a small hump on the dorso-subdistal part ( Fig. 6 View FIG A-D) (vs margin gently curved without any hump, Fig. 4D, E View FIG ).